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Evolution… day 2

Charles Darwin. Alfred R. Wallace. Thomas Huxley. Gregor Mendel. Theo. Dobzhansky. R.A. Fisher. J.B.S. Haldane. Stephen J. Gould. Evolution… day 2. Barbara McClintock. Misconceptions (continued). “THEORY” Evolution is “just” a theory… The theory of evolution is flawed…

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Evolution… day 2

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  1. Charles Darwin Alfred R. Wallace Thomas Huxley Gregor Mendel Theo. Dobzhansky R.A. Fisher J.B.S. Haldane Stephen J. Gould Evolution… day 2 Barbara McClintock

  2. Misconceptions (continued) “THEORY” • Evolution is “just” a theory… • The theory of evolution is flawed… • The theory of evolution is incomplete

  3. Misconceptions “THEORY” • Evolution is “just” a theory… • Theory = a scientifically accepted general principle to describe or explain a particular natural phenomenon

  4. Misconceptions “THEORY” • The theory of evolution is flawed… • Well…not on philosophical or scientific grounds. • When flaws are found, they are used to correct the theory! Scientists in the field don’t debate whether evolution has occurred, but they may disagree on how it happens.

  5. Misconceptions “THEORY” • The theory of evolution is incomplete • Maybe ? • Science works by “self-correcting” over time. • We may not understand all the mechanisms, at this time. • Does NOT equal that we don’t understand most of them! • Newest UPDATE: happening NOW The 2nd Modern Synthesis of Evolution (Taaa…Daaa)

  6. Misconceptions POLITICS • Evolution & Religion • Opposite arguments OR “apples & oranges”? • “Creation Science” & “Intelligent Design” • Are these two different? • Which “creation” do you mean? • What is science and what isn’t…?? • Science seeks explanation in natural phenomena: Supernatural explanations of any type are not options

  7. “Dover Decision”2005 Kitzmiller v. Dover Area School District • Issue started in rural community of Dover, Pennsylvania, and progressed to become a federal court test case for science education. • Dover School Board wanted to require science teachers to offer intelligent design (ID) as an alternative to evolution. • Parents initiated the lawsuit and sought to show that the School Board had religious motivations for teaching ID, who denied the motivation. • Required textbook for ID, Of Pandas and People, had originally been a creationist text. • Judge's decision: Members of the school board had religious motivations for introducing intelligent design into the classroom and that ID was not a scientific theory. http://www.pbs.org/wgbh/nova/teachers/programs/3416_id.html

  8. back to science …

  9. Modern Synthesis • Natural Selection • Genetics: • Mutations • Chromosomal changes • Duplication of a gene or genes • Incomplete reproductive isolation (“hybrids”) • Population size or composition • Immigration or loss of “portions” of original group • Emigration from “outside” sources • Nonrandom mating • Historic Contingency • Random events (e.g., huge meteors! disease! Fast climate change!, etc.)

  10. “1st” Modern Synthesis Natural Selection Genetic mechanisms Population size or composition Nonrandom mating (mate selection) Historic contingencies “2nd” Modern Synthesis adds DEVELOPMENTAL MECHANISMS (Taaa…Daaa !!)

  11. The population genetics approach to understanding evolution emphasizes variations within a species that allow certain individuals to reproduce more. The developmental approach looks at variation between groups and emphasizes actions of ‘regulatory’ genes responsible for formation of shape, tissues, organs, and body parts. This approach is more apt to explain evolutionary novelty and constraint. Think of evolution as “evolving embryos” NOT just adults! Together, population genetics and development make a more complete approach to understanding how evolution happens ( mechanisms).

  12. Phenomenon = Retention of juvenile characteristics = PAEDOMORPHOSIS Chimpanzee Skull Growth Human Skull Growth

  13. “Bottom line” Organic EVOLUTION = DESCENT WITH MODIFICATION

  14. Phylogenetics IN CLASS • Consider the following groups: • MAMMALS • FISH • AMPHIBIANS • BIRDS • REPTILES • Draw a TREE OF LIFE showing the relationships among these groups • You have 5 minutes!

  15. Mammals Birds Reptiles Amphibians Fish Implications: A fish evolved into an amphibian An amphibian evolved into a reptile All Reptiles existed before birds and mammals etc.

  16. Trees inherently represent species (or populations) and thus, each bifurcation represents hypothesized speciation events. Although we can replace “species” with groups of species, the assumption of sharing a most-recent common ancestor must be met (we call this “monophyly” or “one origin”). If a species “splits” (diverges from its past genetic profile), we distinguish descendant “species” from the original ancestor.

  17. Thus, each species or group of species is hypothesized to share a most-recent common ancestor. B and C = “sister” taxa, since they share a most recent common ancestor. A and the ancestor to B+C are “sister” taxa i.e., A + [B+C] And so on…

  18. Reptiles ? Mammals Birds Reptiles ? Amphibians Fish We don’t know enough about the group “reptiles” to place specifically on the tree. We need more information and we ADMIT IT!

  19. What is needed…? • Actually…more data! • CHARACTERISTICS! Shared because primitive = Plesiomorphy Shared because descendant = derived or Synapomorphy (NOT “advanced”) Shared because convergent = Homoplasy

  20. Convergence? BEWARE! Convergence depends on how well the character is defined! Bat wings ≠bird wings ≠ insect wings

  21. What is needed…? • Actually…more data! • CHARACTERISTICS! • More distinctive groups • Outgroup(s) • Monophyletic “in” groups Monophyletic clade = any group with a shared common ancestor GROUP doesn’t include all descendants GROUP doesn’t include a common ancestor

  22. f f f f f f f f MAMMALS Egg-layers, Marsupials, Placentals CROCODILES BIRDS LIZARDS + SNAKES feathers Mammary glands, 3 ear bones Other Dinosaurs TURTLES AMPHIBIANS Frogs, Toads, Salamanders, Caecilians DINOSAURS shell LOBEFINNED FISHES horny scales BONY RAY-FINNED FISHES Amniotic Egg LUNGFISHES CARTILAGE FISHES Chondrichthyes Limbs, 1 Ear Bone “Stirrup” Larynx (from gill bar) PLACODERMS f Lobed Fins JAWLESS FISHES: Ostracoderms f, Lampreys, Hagfishes simple lung Bone, Jaws (from gill bar) Cranium, Brain, Vertebrae

  23. Your homework problem: CHARACTERISTICS A--R

  24. B=1 Step 1 + 2 = using A, B, D and R, you produce this tree: Sally Amber Ronnie Who Carla R=1 OUT Harry Gary Angela Paul D=1 A=1 Step 3 = resolve the groups still clustered

  25. Remember… You also must turn in the topic you have selected for your major paper.

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